Picture reproduction



April 7, 1942. MURPHY 2,278,940

PICTURE REPRODUCTION Filed Jan. 3, 1958 '7 Sheets-Sheet 1 FIG.

mz/Zw/ 43 nv VENTOR RBMURPHY gig W A TTORNEV April 7, 1942. P. B. MURPHY PICTURE REPRODUCTION Filed Jan. 3, 1938 7 Sheets-Sheet 4 /N VENTOR 8y PBMURPHY W A T TORNEY i 7, 1941 P. B MURPHY 2,278,940

PICTURE REPRODUCT ION IS, 1938 7 Sheets-Sheet 6 Filed Jan.

FIG.

INVENTOR PBMURPH V BV ATTOLRNEY Ap 7, 1942. P. B. MURPHY PICTURE REPRODUCTION I5, 1938 '7 Sheets-Sheet 7 Filed Jan.

INVENTOR Pd MURPH V Patented Apr. 7, 1942 2.278.940 rro'roaa REPRODUCTION Paul B. Murphy,

Western Electric Com South Nyack, N. Y., assignor to r y, Incorporated, a

co poration or New York Application January 3, 1938. Serial No. 183,059

8 Claims.

This invention relates to picture reproduction and particularly to apparatus for and methods of producing enlarged paintings of an original picture or design, for example, mural paintings.

An object of the invention is to produce directly upon a desired surface, a wall, for example, a reproduction of an original picture or design which is pleasing and artistic in appearance.

Another object is to produce enlarged paintings of a picture or design upon a plane or somewhat irregular surface in a single color or in a variety of colors upon a desired background color.

In accordance with an embodiment of the invention herein shown and described for the purpose of illustration, there is provided a projector for projecting an enlarged optical image of a picture upon a plane parallel to a substantially plane surface, a wall, for example, upon which the enlarged picture is to be produced. The projecting light beam is preferably interrupted periodically. Adjacent to the wall surface is positioned apparatus for scanning the projected periodically interrupted image to produce an alternating (or pulsating) current modulated with respect to amplitude in accordance with the tone values of the image and for spraying paint or other suitable marking fluid upon the wall, under control of the modulated alter nating current. This apparatus includes a movable carriage upon which is mounted a photoelectric cell for receiving, through a light aperture, light from the elemental areas in succession of the image and also an air brush oi special design for controlling the spraying of paint or other suitable marking fluid upon the wall under control of the image modulated alternating current, the valve for admitting marking fluid to the nozzle of the air brush being alternately opened and closed at a frequency equal to that of the alternating current and by an amount corresponding to the amplitude of the alternating current. If desired, instead of interrupting the light beam which projects the image, there may be provided a circuit including a source of alternating current which is modulated in accordance with the light activation of the light sensi tive scanning element.

In a modified arrangement for producing pictures in colors there is employed a dispersion prism for directing light of different colors projected from the picture to be reproduced to different light sensitive electric elements, respectively. Alternating currents of difi'erent [requencies are modulated under control of differ ent light sensitive elements, respectively, thus producing a plurality of modulated alternating currents, one for each of a plurality of color components. In this arrangement there is provided an air brush of special construction in which a plurality of fluids of difl'erent color, respectively, for example one for each primary co]- or, are mixed prior to being ejected from the nozzle of the air brush, a plurality of valves, one for each coloring fluid under control of dlfierent modulated currents, respectively, being utilized for controlling the amount of each fluid going into the mixture.

In another modified arrangement for reproducing enlarged pictures in a single color or in a plurality of colors, the original picture is projected upon a ground glass screen to produce an image larger than the original but smaller than the enlarged picture to be produced. A movable carriage supports a photoelectric cell mounted in proximity to a scanning aperture for scanning an image formed on the ground glass screen along successive parallel lines, the ground glass screen also being supported by the carriage. For reproducing pictures in natural colors, three separate transparencies made from color separation negatives and each corresponding to a different color are projected upon different ground glass screens, respectively, and the images are separately simultaneously scanned to produce three image currents, one for each of the three color components of the picture to be produced. The carriage carrying the scanning apparatus is driven through flexible shafts and through a variable speed transmission gearing by means of the mechanism for driving the carriage carrying the air brush for reproducing the picture. By varying the speed of the scanning carriage in steps and by varying the size of the images projected upon the ground glass screens, the ratio of the size of the reproduced picture to that of the original can be accurately con trolled.

Referring to the drawings, Fig. l is a side elevation of a picture reproducing apparatus in accordance with the present invention;

Fig. 2 is a rear elevation of a portion of said apparatus;

Fig. 3 is a plan view of the image projecting apparatus-shown in Fig. 1;

Fig. 4 is a diagrammatic showing of the motor reversing mechanism used in the apparatus shown in Figs. 1 and 2:

5 is a detailed sectional view of the air brush shown in Fig. 1;

l-"lg. G is a diagrammatic showing of the movcarriage of Figs. 1 and 2 and the associated -al circuits;

Fig. 7 is a diagram showing the path traced by the image scanning and picture producing apparatus.

Fig. 8 is a schematic showing of a modification of the arrangement according to the preceding figures, adapted for reproducing multicolor pic- Lures;

Fig 9 is a side elevation partly in section of an air brush employed in the arrangement shown in Fig. 8;

Fig. 10 is ai'view partly in section of the air brush as viewed along the line i-Iil of Fig.

Fig. 11 is a plan view of a modified picture reproducing apparatus in which the image scanning device and the picture reproducing device are mounted upon different movable carriages. respectively;

Fig. 12 is a, rear elevation of a portion of the apparatus shown in Fig. 11, parts being broken away to show details of construction;

Fig. 13 is a side view partly in section taken along the line I3l3 of Fig. 12; and

Fig. 14 is an enlarged view showing a detail of the apparatus shown in Fig. 1.

In accordance with the embodiment of the invention shown in Figs. 1 to 6, inclusive, there is provided a picture projector 20 mounted upon rods 2|, which form part of a pedestal 22, the height of which is adjustable. The projector is movable along the rods 2i but it may be locked in position by. the locking clamp 23. The projector comprises a suitable light source 24. condenser lenses 25. aperture screen 26 and objective lenses 21. for projecting an image of the picture 28. The light interrupting disc 29 having a plurality of light transmitting openings 30 therein is driven by a motor iii to interrupt the light beam repeatedly at a rate higher than the rate of seaming the elemental areas in succession of the projected image to introduce a carrier component into the image current.

Adjacent to a surface, such as the wall 40, is positioned an apparatus for producing an enlarged painting of the original picture 28. This apparatus includes a supporting frame Al to which are secured a horizontal track 42 at its upper portion and a lead screw 43 at its lower portion. The vertical tracks M each are secured at their upper end to a member 55 on which are mounted wheels 46, the latter being adapted to ride along the horizontal track H. The lower end of each vertical track is secured to a member 41 which is adapted to be driven horizontallv through the nuts I! in enga ement with the lead screw 13. The carriage 50 is supported by a cable which passes over guide pulleys 52 attached to member l5 and which is wound u upon a drum 53. The carriage 50 is guided between vertical tracks 44 by the wheels 54 secured to the carriage. The drum 53 is driven by a motor 55 first in one directi n and then in the oth r to alternately raise and lower t e carr a e 5 under control of switch 86, shown in detail in F 4. When he carr a e 50 a proaches the upper limit of its travel. the arm 51 attached to carriage 50 engages the arm 58 secured to vert cal rod 59 to raise the rod 59 and th s p rat a switch 6| to re erse the conn c i n fr m battery iii to motor 55. The motor is thus caused to run in the reverse direction to lower the carriage 80. At this time the switch 6i also closes for a short interval a circuit for energizing the winding of stepping magnet 62 by current from battery 63, thus causing the ratchet gear to advance a step and causing the rotation of lead screw 43 to which ratchet gear 65 is attached, to move the vertical tracks H, member 45 and carriage 50 to a new position.

When the carriage 50 approaches the lower limit of its travel, the arm 53 attached to carriage 50 engages arm 64 to lower the rod 59 to the position shown in the drawing. The switch 6| thus reverses the motor 55 and the stepping magnet 53 is thus energized momentarily to cause the tracks 44 to be moved farther along the lead screw 43. When the picture production is completed, the pawl Iii (Fig. 14) may be manually pulled out of engagement with the ratchet B5 and a pin H placed in an opening for holding the pawlout oi engagement. The lead screw may then be turned manually by means of the crank 12 to return the assembly including the vertical rods 44 to its original position. The carriage 50 is provided with a guide wheel 66 for running against the wall surface 6! upon which a painting is to be produced. thus maintaining the nozzle of the air gun properly spaced from the wall.

As shown in Fig 6, one portion 68 of carriage 50 telscopes within the other portion 69 and the springs 10 produce a force between the two portions to maintain the guide wheel 66, attached to portion GB, in contact with the wall 67. The casing 68, 63 forms a lighttight enclosure in which are mounted a light sensitive cell 80, an amplifier stage comprising vacuum tube ill and air brush 82.

In setting up the equipment for operation. the pedestal 22 is moved into position to project upon the wall 61 an image of the size which it is de sired to produce {her on Hill projector 7i? hem at the forward position. The projector tlim: moved along the track 2i away from the wall a certain distance to project an image of the same s ze in a plane parallel to the wall in which lies the rear portion 83 of the carriage 50. Due to the movement of the carriage 50, an aperture 34 therein traces adjacent parallel paths in sucession as indicated diagrammatically by the broken line in Fig. '7. This light from the olementa] areas in succession of the projected image is transmitted through the aperture 84 and is thus dir ted bv a lens 85 upon the light sensitive urface of the photoelectric cell 80. The polarizin battery 86 and resistive element 31 are conn cted in series in the anode-cathode circuit of th photoelectric cell Bil. The light sensitive athode is also connected through a condenser M to the control grid oi vacuum tube 8i and th anode of light sensitive cell 80 is connected to the cathode of vacuum tube 8i. Across the ande-cath de circuit of tube 8i is connected an inmii resistor 89. The output circuit of the amnlifyin vacuum tube 8| comprises the primary indin of transformer 90 and the anode batte ill. The pair of conductors 92 in the cable us c nnect the secondarv windin of transformer 90 n the in ut circuit of an amplifier 9! comprisin -"um tubes 95 and 96. A grid biasin batter" i" is c nnect d in the grid-cathode circuit of uum tube 95 and the anode circuit of th be cflmflris s the primary inding of trammrr 98 and an de battery 99. The seeondarv winding r nsfor er 98 is connected in seri s h the biasin battery 100 to the rid-cathod circuit or vacuum tube 98. the anode circuit of which comprises battery IN and primary winding of transformer I02. The secondary winding of transformer I02 is connected by the pair of conductors I03 of cable 93 to the movable coil I04 of the electrodynamic driving element of the air brush 82. Paint or other marking fluid is supplied to the air brush from a reservoir I and air under pressure is supplied to the air brush through flexible tubing I06. Air under pressure is also supplied to the reservoir I00 through tube I05 :to maintain the marking fiuid under pressure. The cable 93 may have additional conductorsi for supplying heating current for the cathode of tube BI, for example. The purpose of the guide roller 66 in conjunction with the springs is to maintain the orifice I01 of the air brush a fixed distance from the wall 61.

As shown in Fig. 5. air under pressure flows from tube I05 through the passage H0 and through the orifice I01, the air flowing continuously during operation. The liquid coloring fluid under pressure fiows from reservoir I08 into channel III. The opening at one end of channel III is normally closed by tip H2, which is secured to a rod H3. The channel III is closed at the other end by a flexible diaphragm I I4, the central portion of which is secured to rod H3. The moving coil I04 is secured to the central portion of diaphragm II4 and'is positioned bet-ween the pole pieces of the electromagnet II1 having a winding H9. The peripheral port ons of diaphragm H4 and the electromagnet II'I are suitably supported by the outer barrel IIG. as shown in the drawings. Suitable leads connect the moving coil to the terminals I to which the source of picture modulated current is connected and the winding II 4 is connected to terminals I09 to which is connected a source of direct current. The pressure of the coloring liqu d aga nst the one side of diaphragm II4 produces a force in a direction to maintain the channel III normally closed by the tip II2, this force being relatively large because of the relatively large area of diaphragm H4 in contact with the coloring flu d. This force may be so large that the nozzle would not be opened in response to picture current impulses of small amplitude impressed upon the movable coil I04. Means are therefore provided for setting up a variable force acting in opposition to the force produced by the liquid pressure so that the nozzle will be opened in response to small amplitude picture impulses of one polarity and so that the nozzle will be closed in response to the impulses of opposite polarity. For this purpose there is secured to the end of rod H3.

opposite the tip II2, a metal disc I20 to which is secured a helical spring IN. a second disc I22 being secured to the opposite end of the spring. The thumb screw I23 threaded into a tapped porlion of the housing I24 engages the disc I22 for compressing the spring |2I by a desired amount.

The current impressed upon the winding I04 is an alternating current. the frequency or which is equal to the frequency of interruption of the light beam by the light interrupting disc 29, this alternating current being modulated with respect to amplitude in accordance with the tone value of successively scanned elemental areas of the projected image. Each half cycle of one polarity of the current flowing through the winding I04 causes the diaphragm H4 and rod II3 to move in a direction to cause the tip II2 to move away from the end of the passage III, thus permitting marking fluid to flow from the passage III. The passage III isclosed in response to the current Ill impulses of opposite polarity. The streamline shape of tip I I2 permits the current of air which is flowing continually under pressure to carry off and atomize all of the marking fluid liberated by each movement of the tip. Thus the accumulation of drops of marking fiuid which would result in undesirable splotches or irregularities in the reproduced picture or pattern is avoided. The atomized marking fluid is elected from the nozzle I01 upon the wall surface 61 and since the nozzle I 01 is moved along a path like that traced by the image scanning aperture 84. an enlargement of-the picture 20 is painted upon the wall 61.

With a modified arrangement shown in Figs. 8. 9 and 10 pictures or patterns can be produced in a plurality of colors, natural colors, for example. As in the arrangement described above. the projector 20 projects an enlarged image of the picture I and this projected image is scanned by the moving aperture I5| in the carriage 50. The light beam entering the aperture I5I is directed in substantially parallel rays by the lens I52 upon the dispersion prism I 53. The resulting light beams of different colors, respectively, which may be the primary color components, are directed by means of the lenses I54 upon the photoelectric cells I55, I56 and I51, respectively. If desired. instead of employing a prism to separate the light into its color components, a light filter may be used with each photoelectric cell for selecting a desired component of the light beam having all of the color components, this light beam being directed upon the cells through different color filters, respectively. In series with the photoelectric cell I55 there are connected a resistive element I56 and a source of alternating current I59, preferably of a frequency within the audible range. The resistive element I58 and alternating current source I59 in series are connected across the input circuit of the amplifier vacuum tube I60 through a condenser I6I, the usual grid biasing battery I62 and grid leak resistor I53 being provided. Circuits simil r to that connected to the photoelectric cell I55 are connected to the photoelectric cells I55 and I51, these circuits including alternating current sources I10 and Ill, respectively, and vacuum tube amplifiers I60 and IE5, respectively. The sources of alternating current I59, I10 and HI are of different frequencies, respectively. such that they may be separated by tuned circuits or filters after being modulated in accordance with the picture tone values. The anodecathode circuits of vacuum tubes I60, I64 and IE5 are each connected in series with the primary winding of transformer I66 and the anode battery I61. The secondary winding of transformer I66 is connected across the input circuit of amplifier vacuum tube I68 and the output of this amplifier is connected through transformer I69 to the input circuit of a pushpull amplifier comprising vacuum tubes I12 and I13 and output transformer I14. The secondary winding of transformer I14 is connected to the primary windings of transformers I15. I16 and I11 in series, the primary circuits being tuned by means of condensers I18, I19 and I to select, respectively, the currents from sources I59, I10 and HI which are modulated. respectively, in accordance with the tone values of the different color components of the picture. If desired, of course. band-pass filters may be employed instead of the tuned transformer circuits for selecting the image currents corresponding to the different color components of the picture. The

secondary windings of transformers llii, I15 and I11 are connected, respectively, to the windings of the color nozzles m, H32 and I83 of the air gun I84 through the variable resistor elements I05. I80 and IE1, respectively.

The air gun I34 is shown in Figs. 9 and 10. During operation air under pressure is supplied to the air gun and the air flows continuously from tube 206 through the mixing chamber 2l0 and through the orifice 201. The three color nozzles Illi, I32 and I83 are provided, each for supplying color of one of the three color components of the ,picture under control of the corresponding image current from transformers I15. I16 and H1 to the mixing chamber 210. The longitudinal axes of the three color nozzles lie in a plane perpendicular to the axis of the mixing chamber and the axis of each color nozzle forms an angle of about 120 degrees with the axis of each of the other color nozzles. The three color nozzles are alike in construction. Considering the nozzle l8i. the liquid coloring matter is introduced under pressure. due to the supply of compressed air from tube 206 to the color reservoir 208. into channel 2 through the tube 205. The opening at one end of channel 2 is normally closed by tip 2i2 which is secured to a rod H3. The channel 2 is closed at the other end by a flexible diaphragm 2, the central portion of which is secured to rod 2l3. The moving coil 204 is secured to the central portion of diaphragm 2I3 and is positioned between the pole pieces of the electromagnet 2I1 having a winding H9. The peripheral portion of diaphragm H4 and the electromagnet 2i1 are suitably supported by the outer barrel 2H5 as shown in the drawing. The pressure of the coloring fluid against one side of the diaphragm 2l4 produces a force in a direction to maintain the channel 2i! normally closed by the tip 2l2, this force being relatively large because of the relatively large area of diaphragm 2" in contact with the colorin fluid. The means including the spring 22i is provided for opposing the force due to the fluid pressure so that the resultant force tending to maintain the tip 2l2 in closed position when no picture current is impressed upon the coil 204 may be adjusted to a desired value as explained in connection with the above description of Fig. 5.

Each half cycle of one polarity of the current flowing through the winding 2 49 causes the armature 2IB to be attracted and the tip 2i2 to move away from the end of passage 2 by an amount dependent upon the amplitude oi the current flowing through winding 2l9, thus permitting coloring fluid to flow into the mixing chamber H0. The three fluids of different color. respectively supplied in varying portions by the color nozzles IBi, I02 and 133. are mixed and atomized in the chamber 2l0 and elected from thq hozzle 201 upon a wall or other suriace to reproduce the picture I50 in colors.

In Figs. 11, 12 and 13 is shown a modification oi the apparatus shown in the preceding figures for producing mono-color or multi-color paintings. This apparatus is particularly adapted for use in locations where there is insuflicient space to permit the projection of an image of the size of the picture to be produced. Also, the apparatus is of such size that a suitable enclosure may be provided for the picture projector and picture scanning apparatus so as to prevent extraneous light from reaching the photoelectric cells when reproducing multi-color images.

Three picture projectors 30L 302 and 303. like the projector 20 of Fig. 1. are provided each for projecting from a transparency made iros. color separation picture negative. When it is r;-; sired to reproduce a picture in a single color, oi course. it is necessary to use only one 01. the projectors. The projectors project images 01' a size larger than the original but smaller than thr picture to be produced. upon the ground glass screens 304, 305 and 300, respectively. Photo-- electric cells 301. 300 and 309 are provided for scanning the three projected images, the cri being positioned within enclosures 3H. 3i2 and 3l3, respectively. each enclosure having a scanning aperture 3 therein for admitting light to the enclosed photoelectric cell from the elemental areas in succession of the projected image. The screens and photoelectric cell enclosures are mounted on a suitable traveller which is a modification of a conventional lathe bed and lead screw arrangement. As shown in the drawing the screens 304. 305 and 308 and the photoelectric cell enclosures 3H. 3l2 and 3I3 are rigidly sup ported by a rod 3i5, one end of which terminates in a nut 3H5 which engages a lead screw 31'! supported by the housing M9. The rod 3! which is rigidly supported by the housing 3i9 passer through an opening in a projecting portion r the nut 3i6 for maintaining the nut 3H5 in props alignment with the lead screw 3H.

The screens 304. 305 and 308 and the phci' electric cell housings 3| i,3l2 and 3l3 are mov. vertically due to the rotation screw 3i1. Ho zontal motion is imparted to these elements d1. to the rotation of the lead screw 320 which supported by the housing 32!. For this purpos there is secured to the apron portion 322 of th housing 3i9 a member 323, the jaws 324 and 32 of which when closed by the action of spring 32' form a nut which engages the lead screw 32 The nut may be moved out of engagement wittthe screw 320 by pulling the wheel 32'! forwardly. as viewed in Fig. 12. This pull causes th shaft 323 to which the wheel 321 is secured t be moved toward the left as viewed in Fig. l: and due to this movement of shaft 328, the coils. 329 attached to shaft 328 engages one end of th: bent rod 330 to cause the jaws 324, 325 to open The movement of shaft 328 also brings the pinio: 33l which is mounted upon the shaft into engagement with the rack 332. thus permitting ti housing 3i9 together with the screens 304. 3i. and 306 and the photoelectric cell housings 3|: 3l2 and 3l3 to be moved manually in a hOl'izontal direction by turning the wheel 321.

The apparatus for reproducing a picture under control of photoelectric cells 301, 308 and 309. shown in the upper portion of Fig. 11, is similar to the apparatus disclosed in Figs. 1, 2, 4, 9 and 10. The carriage 340 carries an air brush similar to the air brush I04 shown in Figs. 9 and 10 and having a nozzle 3. The carriage is moved vertically by means comprising a motor 339 and a cable drum 342, like the motor 55 and the cable drum 33. respectively, of Fig. 2. The car-- riage is moved horizontally by means cornpris ing a lead screw 343, not shown, like the leac screw 43 of Fig. 2. and a stepping magnet 3-H like the stepping magnet 62 of Figs. 1, 2 and 4. The ratchet wheel 338 is secured to one end of lead screw 343. The photoelectric cells 301, 308 and 309 are connected to the input of an oscillator-modulator circuit 345, the output of which is connected through an amplifier-filter circuit 346 to the windings of the air brush having nozzle 34L The circuit arrangement connecting the photoelectric cells with the air brush may be substantially as shown in Fig. 8.

The lead screw 328 is driven by the stepping magnet 34% through a flexible shaft 24? connected to the shaft 343 at one end and to the shaft 8 and the variable speed transmission gearing 349 at the other end. The transmission gearing may be of any well-known construction and includes a gear shiit lever 350 for effecting a change in gear ratio so that the rate of movement of and, therefore, the distance of travel of, the screens 304, I05 and 30B and their associated phbtoelectric cells in a horizontal direction may be varied with respect to the horizontal motion of carriage 348. The lead screw 3" is driven through a variable speed transmission gearing similar to the gear 349 and through flexible shaft 35i by the motor 34!.

In operating the apparatus of Figs. 11. 12 and 13, the three transparencies made from color separation negatives corresponding to diiierent primary color components, for example, are positioned in different projectors 30L 302 and 303, respectively. The projector are adjusted so as to focus the images of the transparencies upon the ground glass screens 3, 305 and 305, re spectively. The use of ground glass permits the images to be viewed from the side opposite the side upon which the images are projected and provides a surface on which pencil marks can be made and later erased. By operating the wheel 3 the arrow on the lower edge of the apron 322 can be brought into alignment with any of the three marks upon the housing 321. The distances between equal to the distances between the centers of the scanning apertures 3 of the photoelectric cell housing 3", 3|! and M3. By means or these markings and a sharp pencil outline of some part of the image which shows on all three transparencies, exact positioning of the projectors so as to secure registration of the images can be obtained. In operation the entire framework carrying the screens 304, 305 and 306 and the photoelectric cells and housings moves up and down and advances horizontally at the end of each vertical movement. In this manner the scanning apertures 3| will simultaneously scan images projected from the color transparencies by the projectors till, 302 and 303, respectively. The movement of the air brush carriage 340 will be at all times in the same direction relatively as that of any of the photoelectric cell housings 3H but the carriage 340 will be moved through a relatively greater distance. Thus the reproduced image will be larger than the projected image which is scanned, the latter in turn being an enlargement of the original picture transparency from which the image i projected. For producin: images in a single color obviously only one of the projectors need be used for projecting the image. i

It may be desired to provide 1 r a larger number of enlargement ratios than can be obtained with a practical number of fixed gear ratios. With the apparatus shown in Figs. 11, 12 and 13 enlargement ratios between the variable fixed steps can be provided by moving the three proiectors so as to project a scanning image of an exact size which when enlarged by one of the variable fixed gear ratios will provide a reproduced image of exactly the size desired. Because of the distance between the projectors and the scanning areas it will be possible to set up any desired masking or vlgnetting scheme in order these markings are made to provide for double printing oi parts of more than one transparency on a given area of reproduction. Also the entire scanning equipment described can be made small enough in size so that the entire unit can be covered by a collapsible shield which is substantially light-proof. The flexible shafts 341 and 35! may be replaced, it desired, by suitable interlocking motor systems.

The system shown in Fig. 6 is adapted for transmitting from a negative transparency, that is, when large amounts of light intermittently reach the photoelectric cell 80, an alternating current of large amplitude is produced for energizing the winding of the electrically controlled valve of the air brush I04 and a large amount of marking fluid is ejected from the air brush. The arrangement shown in Fig. 8, on the other hand, is adapted for transmitting from a positive transparency since, when a large amount of light reaches the photoelectric cell I55, the amplitude of the alternating current produced for energizing the air brush "II is small and a small amount of pigment is ejected from the air brush. This arrangement obviously can readily be modified for transmitting from a negative, for example, by connecting only the resistive element I 58 across the input circuit of vacuum tube I60 instead of the resistive element I58 and the alternating current source I59 in series.

In addition to producing mural paintings upon walls, the apparatus may be used, for example, for producing special patterns upon dress goods, draperies, upholstery materials, leather for fancy shoes, purses, etc., fabric for wall decoration, wall paper, background scenes for motion picture sets, stage scenery and special advertising posters.

What is claimed is:

1. Picture producing apparatus comprising an air brush having an electrically operated valve {or regulating the fiow of marking fluid thereto, and means for impressing upon said valve 21 peliodl'cally varying current modulated with respect to amplitude in accordance with tone values of successive elemental areas of a picture.

2. Picture producing apparatus comprising an air brush having an electrically operated valve for regulating the flow of marking fluid thereto, said valve being opened by varying amounts in accordance with the amplitude of the energizing current supplied thereto over a range of current amplitudes, and means for supplying to said valve, for operating it, periodically recurring current impulses of amplitudes within said range separated by intervals during which the current has an amplitude outside of said range.

3. Picture producing means comprising a source of alternating current modulated in accordahce with the tone value of successively scanned elemental areas of a picture, an air brush having an electric valve for controlling the amount of marking fluid supplied thereto, and means for supplying modulated alternating current from said source to said valve for operating it.

4. Picture producing apparatus of the type employing an air brush supplied with a plurality of marking fluids of different characteristics, respectively, comprising a support, a plurality of semi'transparent screens and a plurality of light sensitive scanning means, one for each screen, fixedly mounted upon said support, means comprising a lead screw for causing the movement or said support in response to the rotation of the screw about its axis, means comprising a second lead screw for causing a movement of the first lead screw in a direction substantially perpendlcular to its axis, means for projecting images to be scanned upon said screens respectively, means comprising said light sensitive means for controlling the supply of said marking fluids to said air brush, and means for causing said air brush to be moved along a path corresponding to the path over which any one of said scanning means is moved but at a relatively higher rate so that/the air brush traverses a larger area than that traversed by one or said light sensitive means.

5. Image producing means comprising a source of current having variations representative of tone value of successive elemental areas of a picture to be produced and also periodic changes in amplitude not representative of picture tone value, an air brush having an electrically con trolled valve for controlling the ejection of marking fluid therefrom, and means for impressing current from said source upon said valve to cause it to respond to all of said variations.

6. Apparatus for producing a picture record of an image projected thereon comprising a carriage having an. aperture therein for receiving light from a portion of the projected image. a light sensitive device for receiving the light transmitted through said aperture mounted upon said carriage, an air brush mounted upon said carriage having an electrically operable valve 1 or controlling the amount of marking fluid ejected from the nozzle of said air brush upon said record surface, a transmission circuit at least a portion of which is mounted upon said carriage for electrically connecting said light sensitive device with the valve of said air brush, a track for guiding the movement oi said carriage, means for causing the carriage to move along said track alternately in opposite directions. a second track for guiding the movement of said first track in a direction transverse to the direction or movement of said carriage along said first track, and means for causing a movement of said first track for each reversal in the direction of movement of said carriage.

7. Apparatus for producing pictures in a plurality of colors comprising a substantially lighttight carriage having a scanning aperture therein, a plurality of light sensitive means mounted within said carriage for receiving light of difierent color components respectively of the light transmitted through said aperture and for setting up picture currents corresponding to the difierent color components respectively, means for producing a visual indication in response to said picture currents and varying in accordance with the variations of said currents, said means being mounted on said carriage, and means for transmitting said picture currents to said indication producing means. at least a portion of said transmission means being mounted upon said carriage.

8' Picture scanning apparatus comprising a support, a semi-transparent screen mounted upon said support, means for projecting an image upon said screen, a light sensitive means mounted upon said support in fixed relation to said screen, means for moving said support alternately in opposite directions, and means for intermittently moving said support in a direction substantially perpendicular to said first-mentioned directions.

PAUL B. MURPHY. 

